How about if someone farts into a microphone and runs it through a harmonizer (to make it deeper) and distortion. That would go really well with brutal/slam death!
I don't know if this has been done. But a band that plays as fast as possible all the time. And by that I mean NOT just the drums (a lot of bands just have superfast drums to tremolo riffs that really aren't that fast in that they don't switch from note to note fast at all). I'm talking about fast as in different notes are played so fast it almost sounds like a blur. Some early Sinister riffs approach this (Perennial Mourning, Awaiting the Absu, etc.) and some of In Battle's and Mjonir's work does as well, but it isn't constant, and not quite as fast as what I'm talking about would be.